234 Mr GRAHAM on the Law of 



generally so minute, that they might be neglected with impunity. 

 Corrections for temperature and pressure might therefore be dis- 

 pensed with, which was a great advantage. 855 measures hy- 

 drogen were found eventually to be replaced by 226.5 measures 

 air, both saturated with vapour at 62. 



QKK 



2gg-g = 3.774 diffusion-volume of hydrogen. This deter- 



mination is somewhat below the theoretical diffusion-volume, 

 3.79, while the preceding determination was in excess. 



Experiment 3. Another diffusion-instrument of the form 

 B, with a dense plug, one-tenth of an inch in thickness, was 

 filled with water, which was then poured into a counterpoised 

 phial, and found to weigh 1085.7 grains. When filled over wa- 

 ter, 1085.7 grain-measures of gas are therefore introduced into 

 this instrument, and in this way we express most correctly its 

 capacity. The instrument, after the plug was dried, was entirely 

 filled with hydrogen gas, as in the preceding experiment, ther- 

 mometer 61. The bulk of the diffusion appeared to be over in 

 an hour and a half, but five hours were allowed to the experi- 

 ment. Thereafter the water which had entered the instrument 

 was poured into a counterpoised phial, and found to weigh 800.6 

 grains. This last quantity represents the contraction, and sub- 

 tracting it from 1085.7, we have the return-air equal to 285.1 

 grain measures. Now, 



1 f\Off W 



l rr 3.808 diffusion- volume of hydrogen gas. 



Experiment 4 Same bulb, circumstances the same, but 

 thermometer 62. Time allowed for the diffusion four hours. 

 1085.7 measures hydrogen were replaced by 286.1 measures 



air. 



1085.7 



"= 3.795 = diffusion-volume of hydrogen. 



